Avascular Necrosis (AVN): The Complete Guide — Causes, Stages and Treatment
Avascular necrosis (AVN), also called osteonecrosis, is the death of a segment of bone caused by loss of its blood supply. It most often affects the femoral head — the ball of the hip joint — and, unlike ordinary arthritis, it is largely a disease of working-age adults in their 20s, 30s and 40s. Caught early on MRI, before the bone collapses, joint-preserving surgery is often possible. Caught late, the realistic option is usually hip replacement. This guide explains the causes — steroids (including post-COVID steroid courses), alcohol, trauma and sickle cell disease — the Ficat and Arlet stages and what each one means for treatment, why an early MRI matters so much, and the myths that cost patients their window.
What avascular necrosis actually is — and who it affects
Bone is living tissue that depends on a steady blood supply to stay healthy. When that supply to a specific segment of bone is interrupted — by blockage of small vessels, injury, or rising pressure within the bone itself — the bone cells in that area begin to die. That is what the name describes: avascular means "without blood supply", necrosis means "tissue death". Left unaddressed, the weakened segment loses its structural support and can collapse under normal load, damaging the joint surface above it.
The hip — specifically the femoral head, the ball at the top of the thigh bone — is by far the most commonly affected joint, because its blood reaches the ball through a narrow corridor of small vessels with very little backup circulation. AVN can also affect the shoulder (humeral head), the knee (femoral condyle), the ankle (talus) and, less commonly, the wrist and jaw.
Two facts about who gets AVN shape everything else in this guide. First, it strikes young: the typical hip-AVN patient is 25 to 45 years old — someone with decades of working, walking life ahead, which is exactly why preserving the natural joint matters so much. Second, in non-traumatic AVN it frequently involves both hips — the causes act on the whole body, not one joint — so when AVN is found on one side, the other hip is imaged too, because it may be at an earlier, still-treatable stage.
The typical story is months of unexplained groin or thigh pain, worse on walking or standing, sometimes felt mainly in the knee (hip problems commonly refer pain down to the ghutna). Many patients are treated for "muscle pull", "sciatica" or કમર (back) trouble first, because the early X-ray looks normal. Reaching a હાડકાના ડોક્ટર (bone doctor) after that detour, with the pain unexplained and the X-ray "clear", is a recognisable AVN story — not a rare one. In Hindi the condition is often described to patients as कूल्हे की हड्डी में खून की सप्लाई रुक जाना — the blood supply to the hip bone getting cut off — which is exactly what it is.
What causes AVN — an honest list
AVN is not caused by anything a patient did "wrong", and several of its major causes are the after-effects of necessary medical treatment. What matters is recognising the risk factors, because they decide who should be investigated early.
Corticosteroid (steroid) use — including post-COVID
Prolonged or high-dose steroid therapy — for lupus, kidney transplant, asthma, severe inflammatory or respiratory disease — is one of the most consistently identified causes of AVN. In India this gained new attention after the pandemic: hip AVN has been reported in patients who received corticosteroids during COVID-19 treatment, described in a published case series by Agarwala and colleagues in BMJ Case Reports (2021), and orthopaedic surgeons across the country have seen such cases since.
Two things are true at once: steroids saved lives in severe COVID, and anyone who needed significant steroid doses and now has persistent hip, groin or thigh pain deserves an MRI rather than reassurance on a normal X-ray. See the dedicated post-COVID AVN guide.
Heavy alcohol use
Chronic heavy alcohol use is independently associated with AVN, most likely through its effects on fat metabolism — fatty deposits blocking the fine vessels that feed bone — and on the vessels themselves. The risk builds with sustained, long-term intake. This is asked about matter-of-factly in the history, without judgement, because it changes what should be investigated.
Trauma — fracture or dislocation
A hip dislocation or a fracture of the femoral neck can tear or kink the small vessels supplying the femoral head directly. AVN can then develop months to two years after the original injury has otherwise healed — which is why a hip that was injured, treated and "fine" deserves prompt attention if pain returns later.
Sickle cell disease — a South Gujarat reality
Sickle-shaped red blood cells can block the small vessels supplying bone, making AVN a well-recognised complication of sickle cell disease. Sickle cell trait and disease have documented prevalence in specific communities across South Gujarat — the region's tribal-belt districts are among those prioritised by the Government of India's National Sickle Cell Anaemia Elimination Mission for exactly this reason. So in Surat and surrounding districts this is asked about directly, and where relevant tested for — not treated as a rare or foreign diagnosis — when a patient presents with AVN-pattern pain.
Other medical causes
A cluster of less common causes shares the same mechanism of small-vessel blockage or bone-cell injury: autoimmune diseases such as lupus (both the disease and the steroids used to treat it), organ transplantation, radiotherapy and some chemotherapy, Gaucher disease, clotting disorders, and decompression illness in divers. If one of these applies to you, unexplained joint pain deserves early imaging.
Idiopathic — no identifiable cause
In a meaningful proportion of cases, careful history-taking finds no steroid use, no alcohol excess, no trauma and no blood disorder. This is labelled idiopathic AVN. It is managed exactly the same way — by stage — and having no identifiable cause does not make the condition any less real or any less urgent to stage properly.
The Ficat and Arlet stages — and what each one means for treatment
AVN of the hip is most commonly staged with the Ficat and Arlet classification (often shortened to Ficat; the newer ARCO system maps closely onto it). The stage describes how far the dead segment has progressed — from changes visible only on MRI to full collapse of the joint. The stage at diagnosis, more than the diagnosis itself, decides which treatments are still realistic.
| Stage | What imaging shows | What it means | Realistic treatment options |
|---|---|---|---|
| Stage I | X-ray normal. MRI shows marrow changes and the early necrotic segment. | Bone cells are dying but the ball is still perfectly round. The disease is invisible except on MRI — and often only mildly painful, or silent. | The widest window. Core decompression, with or without bone grafting or marrow-cell techniques; addressing the cause (steroid review with the treating physician, alcohol cessation, sickle cell management); protected weight-bearing while a plan is made. |
| Stage II | X-ray now abnormal — patchy dense (sclerotic) and clear (cystic) areas in the femoral head — but the head's outline is still round, with no collapse. | The dead segment is remodelling, but the joint surface is intact. Still pre-collapse — still the joint-preserving window. | Core decompression with or without grafting remains appropriate for suitable lesions; realignment osteotomy in selected cases. Size and location of the lesion on MRI drive the choice. |
| Stage III | The crescent sign — a thin dark line just under the joint surface where the dead bone has fractured — with or without early flattening of the head. | The turning point. The subchondral bone has collapsed; the round ball is starting to flatten. Results of preservation surgery fall sharply from here. | An honest, individualised conversation. In young patients with small, early collapse, grafting or osteotomy is sometimes still discussed; for many, total hip replacement becomes the more reliable option. |
| Stage IV | Collapsed, flattened femoral head with narrowing of the joint space and arthritic change on the socket (acetabular) side too. | The joint surface is destroyed and secondary arthritis has set in. Joint-preserving surgery can no longer restore the shape of the ball. | Total hip replacement is the standard, evidence-based option, and reliably relieves pain and restores function. Bearing choices for younger patients are discussed on the hip replacement page. |
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What the crescent sign means. The dead bone just beneath the cartilage surface eventually fractures under load, leaving a thin crescent-shaped gap on the X-ray. It is the radiological line between "the ball is still round" and "the ball has begun to give way" — which is why Stage II and Stage III, one stage apart, lead to such different conversations.
Staging is the start, not the whole answer. Treatment decisions blend the stage with the size and location of the lesion on MRI, whether one or both hips are involved, your age, your symptoms, and your general health. Two patients at the same stage can reasonably receive different recommendations.
Why "your X-ray is normal" is not the end of the question
The single most consequential fact in all of AVN care is this: X-rays are frequently normal in Stage I and early Stage II — the exact stages at which joint-preserving treatment works best. The bone changes of early AVN simply are not visible on plain film. MRI, by contrast, detects AVN reliably before any collapse has occurred.
The rule worth remembering: if you have any AVN risk factor — significant steroid exposure (including during COVID treatment), heavy alcohol use, a previous hip injury, or sickle cell disease or trait — and you have unexplained groin, hip, thigh or knee pain, a normal X-ray should not close the case. An MRI is the appropriate next step.
The economics point the same way as the medicine. An MRI of the hips costs a small fraction of any surgery — and the window it can catch is the difference between a day-care joint-preserving procedure and a lifetime managed around an artificial joint that may need revision decades later. In a disease of 30-year-olds, buying time for the natural joint is the whole game. Months lost to repeat X-rays, painkiller courses and unproven remedies are, in a real sense, the most expensive part of AVN.
One practical trap deserves its own sentence: hip AVN can present as knee pain, because the hip refers pain down the thigh — so a young patient with knee pain, normal knee scans and a risk factor should have the hip examined and imaged.
Joint-preserving surgery versus replacement — by stage, honestly
Core decompression is the workhorse of early-stage treatment. One or more narrow tracks are drilled into the dead segment, relieving the raised pressure inside the bone and creating channels through which new blood vessels can grow in. It is a comparatively small operation — typically a short hospital stay — and it is most effective in small, pre-collapse lesions (Stage I–II). It is often combined with bone graft or bone-marrow-derived cells placed into the drilled track; these additions are used in practice and are the subject of ongoing research, and it is fair to say the evidence for the drilling is more established than the evidence for any particular additive.
Bone grafting procedures go a step further: the dead segment is cleared and packed with graft, and in selected young patients a vascularised fibular graft — a piece of the leg's fibula bone moved together with its own blood vessels — is used to bring both structure and blood supply into the femoral head. These are larger operations with longer recoveries, reserved for carefully chosen cases. Realignment osteotomy takes a different approach: the femur is cut and rotated so that an undamaged part of the ball carries the body's weight, moving the dead segment out of the load-bearing zone; it suits particular lesion sizes and positions. Osteotomy around the knee is discussed on the knee page.
What no treatment can do: no medicine, injection, oil, or therapy has been proven to bring dead bone back to life or restore a collapsed femoral head. Tablets such as bisphosphonates have been studied with mixed results and are not a substitute for staging and a surgical opinion. The danger of unproven remedies is not usually the remedy itself — it is the six to twelve months of Stage II becoming Stage IV while relief is awaited.
Total hip replacement is the standard answer once the head has collapsed (late Stage III and Stage IV) — and it is a good answer: it reliably relieves pain and restores near-normal daily function, and modern bearing surfaces are chosen specifically with younger patients' decades of use in mind. Choosing replacement at the right stage is not a failure of treatment; at Stage IV it is the evidence-based treatment. What surgery involves, recovery timelines and implant choices are covered on the hip replacement page, and package pricing at Mahavir Hospital on the hip replacement cost page.
Six AVN myths that cost patients their window
"A normal X-ray means the hip is fine."
The most expensive myth in AVN. X-rays are frequently normal in Stage I–II — precisely when joint-preserving treatment works best. With risk factors and unexplained pain, MRI is the test that answers the question.
"AVN only happens to heavy drinkers."
Alcohol is one cause among several. Steroid treatment for medical illness, trauma, sickle cell disease and idiopathic AVN — with no cause at all — together account for a large share of cases. AVN carries no verdict about how anyone lived.
"Massage, oils or ayurvedic courses can regrow the bone."
No remedy of any system has been shown to restore blood supply to dead bone or to reverse collapse. The harm is the time: months spent on unproven treatment are months in which a preservable Stage II hip can become a Stage IV hip that only replacement can help.
"AVN always ends in hip replacement, so why hurry?"
Backwards on both counts. Caught pre-collapse, joint-preserving surgery can delay or avoid replacement — and the reason to hurry is that this option expires. The fatalism becomes self-fulfilling only when diagnosis is late.
"I'm too young for this to be serious."
AVN is a young person's disease — the typical patient is 25 to 45. Being young is not protection; it is exactly why the diagnosis deserves urgency, because the joint being protected has to last decades.
"The pain settled, so the disease must have stopped."
AVN pain can wax and wane while the structural damage progresses silently — and the opposite hip can be involved without any pain at all. Improvement in symptoms is welcome, but only follow-up imaging can say what the bone is doing.
Frequently asked questions — avascular necrosis (AVN)
What is avascular necrosis (AVN)?
Avascular necrosis — also called osteonecrosis — is a condition where a segment of bone loses its blood supply and the bone tissue begins to die. Without blood flow, the affected bone weakens and can eventually collapse under normal weight-bearing load. It most commonly affects the femoral head, the ball at the top of the thigh bone (hip AVN), and mainly affects working-age adults in their 20s to 40s. It can also occur in the shoulder, knee, ankle or wrist.
What causes avascular necrosis?
The most commonly identified causes are prolonged or high-dose corticosteroid (steroid) use — for conditions such as lupus, kidney transplant, severe inflammatory or respiratory disease — and heavy, sustained alcohol use. Trauma, hip dislocation or a femoral neck fracture can disrupt the blood supply directly. Sickle cell disease is a well-documented cause, particularly relevant in parts of India including South Gujarat, where sickle cell trait and disease have documented prevalence in specific communities. In a meaningful proportion of cases no cause is found — this is called idiopathic AVN.
Can steroids given for COVID-19 cause AVN?
Corticosteroids were a life-saving part of treatment for severe COVID-19, and for most people short courses cause no bone problems. However, AVN of the hip has been reported after steroid treatment for COVID-19 — including a published case series by Agarwala and colleagues in BMJ Case Reports (2021) — and orthopaedic surgeons across India have since seen such cases. Anyone who received significant steroid doses during COVID treatment and now has persistent groin, hip or thigh pain should be evaluated, with MRI if the X-ray is normal, rather than waiting. See the post-COVID AVN guide.
Is avascular necrosis more common in people with sickle cell disease?
Yes. Sickle cell disease causes abnormally shaped red blood cells that can block small blood vessels, including those supplying bone, making AVN a recognised complication. South Gujarat, including the Surat region, has documented sickle cell prevalence in certain communities — the region's tribal-belt districts are among those prioritised by the Government of India's National Sickle Cell Anaemia Elimination Mission — so a history of sickle cell disease or trait is a relevant, direct question when AVN is suspected in a patient from this region, not one to overlook.
What are the stages of AVN and why does staging matter?
AVN is staged using the Ficat and Arlet (Ficat) classification, from Stage I (early bone changes visible only on MRI, X-ray still normal) through Stage II (X-ray changes but no collapse), Stage III (subchondral collapse — the crescent sign — with early flattening of the head) to Stage IV (collapse with secondary arthritis of the whole joint). Staging matters because it determines which treatments remain realistic: joint-preserving procedures such as core decompression work best in Stages I–II, before collapse. Once significant collapse has occurred (late Stage III and Stage IV), hip replacement typically becomes the more appropriate option.
Can avascular necrosis be treated without a hip replacement?
Often, yes — if it is caught before the joint surface collapses. In Stages I–II, joint-preserving options include core decompression (drilling into the dead segment to relieve pressure and stimulate new blood vessel growth), core decompression combined with bone grafting, and in selected cases realignment osteotomy. These aim to delay or avoid replacement; they do not guarantee it will never be needed, and suitability depends on the size and location of the lesion, assessed on MRI. Once significant collapse has occurred, joint-preserving surgery is unlikely to restore meaningful function and replacement becomes the realistic, evidence-based path.
Can AVN affect both hips?
Yes, and it commonly does in non-traumatic AVN — the causes (steroids, alcohol, sickle cell disease) act on the whole body, not one joint. The second hip may be at an earlier, silent stage when the first becomes painful. This is why both hips are routinely imaged when AVN is diagnosed on one side: catching the opposite hip at Stage I–II can open joint-preserving options there even if the painful side already needs more.
Is AVN the same as arthritis?
No. Arthritis (osteoarthritis) is gradual wearing of the joint cartilage, usually in older age. AVN is death of a segment of the underlying bone due to lost blood supply, typically in much younger patients. The confusion arises because late-stage AVN causes secondary arthritis once the collapsed bone damages the joint surface. The distinction matters: early AVN has joint-preserving surgical options that ordinary arthritis does not, and AVN in a 30-year-old is managed very differently from osteoarthritis in a 65-year-old.
Suspect AVN, or already have a diagnosis?
Message on WhatsApp with your reports (X-ray and MRI, if you have them) and questions, or book a consultation directly. For hip AVN specifically, the Surat-focused staging and treatment guide goes into more clinical detail.
Go deeper
AVN of the hip in Surat — the Surat-focused treatment page, plus ગુજરાતી and हिन्दी versions. Post-COVID AVN of the hip covers steroid-related AVN after COVID treatment specifically. If replacement becomes the appropriate option: hip replacement surgery and hip replacement cost in Surat. For AVN affecting the knee, joint-preserving osteotomy is discussed on the knee replacement page. To find the right kind of orthopaedic doctor for your stage of AVN, see finding the right orthopaedic doctor in Surat.